The present invention relates to methods for forming a metal layer on an integrated circuit, and more particularly, to methods of forming a metal wiring layer on a highly-integrated integrated circuit device.
Integrated (semiconductor) circuits are widely used in consumer and commercial applications. As the integration density of integrated circuit devices continues to increase, it is increasingly difficult to form high-density interconnections, also referred to as wiring layers, on integrated circuits. These wiring layers generally have a multi-layered structure. As the metal wiring layer is generally used to transmit electrical signals, it is desirable to provide a metal wiring layer having a low electric resistance and a high reliability.
As integrated circuit devices become more highly integrated, the feature sizes decrease and a width and thickness of the metal wiring layer and the size of included contact holes may decrease. As feature sizes of the integrated circuit device decrease, such, as the width of a circuit line, it typically becomes more difficult to form the metal wiring by etching a metal film. Furthermore, it may be desirable to minimize the thermal budget (i.e., amount of thermal processing) imposed by backend process(es) used in manufacturing the highly-integrated device. If the thermal budget in the backend process(es) increases, the electrical characteristics of the resulting integrated circuit device, such as capacitor characteristics, may be degraded.
Aluminum (Al) is widely used as a material for the metal wiring layer of an integrated circuit device. In forming an Al metal wiring layer, it is generally important to fully fill up included contact hole(s) connecting conductive layer(s) at a lower layer of the integrated circuit device with the Al wiring layer located on a higher layer than the conductive layer(s) so as to electrically connect the conductive layers.
Various approaches are known to improve device electrical characteristics and to fully fill such contact holes between layers (as used herein, the term “contact hole” includes via holes) and/or trenches with aluminum. However, as circuit density increases, for example, to require a metal wiring layer having a circuit line width less than 0.25 micrometers (μm), the aspect ratio of the contact hole or trench increases. As a result, the difficulty of fully filling the contact hole and or/trench with Al by using a physical vapor deposition (PVD) type process, such as a sputtering method, may increase.
One known approach to this problem is to first form a barrier metal film and then to form the aluminum film on the barrier metal film using physical vapor deposition. After forming the aluminum film, a reflow process is used to finish forming of the aluminum wiring layer in the recess region, such as the contact hole. The reflow process is a thermal process in which sufficient heat is applied to the Al film to thermally flow the Al film to improve fill of the recess region. However, to flow the aluminum, the reflow process is generally performed at a temperature of about 500° C. As a result, the reflow process adds a thermal budget to the process for manufacturing the metal wiring layer.